Project Summary/Abstract The intensity of oral cancer pain is higher than other cancers. Quality of life for oral cancer patients is the lowest of all cancer patients because uncontrolled pain interferes with necessary oral functions including eating, talking and swallowing. Exogenous opioids are minimally effective for this type of pain and have significant side effects. Our long-term goal is to develop an effective and safe treatment for oral cancer pain. We recently demonstrated that OPRM1 (the gene for the -opioid receptor) is methylated and down regulated in oral cancer compared to matched normal tissues in the same patients; these patients reported pain at the site of cancer. We further demonstrated that OPRM1 re-expression with viral transduction significantly reduced cancer pain in a mouse model. Expression of the -opioid receptor on the cancer led to the secretion of opioids into the cancer microenvironment. Drawbacks of a viral transduction approach are that viral gene delivery has safety concerns and limited carrying capacity. To overcome these barriers we developed two non-viral hybrid vectors. The first is composed of a cell-permeable peptide (HIV-1 Tat peptide sequence modified with histidine and cysteine residues) combined with a cationic lipid. The second vector substitutes cationic polymer for the lipid. The vectors have excellent transfection efficiency with minimal cytotoxicity in vitro and in vivo. Moreover, the non-viral vectors preferentially transfects oral cancer cells compared to normal cells. Based on our preliminary work we hypothesize that re-expression of the OPRM1 gene within oral cancer using our non-viral vectors will attenuate cancer pain and restore orofacial function without excessive toxicity. In Specific Aim 1 we will d etermine the efficacy of ex vivo OPRM1 gene transfer with non-viral vectors to attenuate cancer-induced pain. Our goal is to move our method of non-viral transfection to the clinic. We foresee clinicians directly inoculating our non-viral vector into an oral cancer. Therefore, in Specific Aim 2 we will determine the feasibility and efficacy of in vivo OPRM1 gene transfer (i.e., directly into the tongue cancer) with non-viral vectors for attenuation of cancer-induced pain. Because our prerequisites for a clinical trial are toxicity and safety studies in Specific Aim 3 we will analyze toxicity and immune response in the cancer mice treated with non-viral OPRM1 gene delivery. The proposed research is significant because we will use a local delivery technique directly into the cancer to reduce the potential side effects of systemic drugs. Our approach is innovative because we will transduce the cancer cells for the treatment of cancer pain. facilitate the development of an effective therapy to treat cancer pain. Ultimately, these studies might